Tarik,
It's hard for me to comment because the car came with the relocation kit fitted, so I never experienced the car without it.
To me, it makes sense to reposition the filter at the front of the car where it can 'breath' better, plus it moves the weight of the battery further back towards the wheel, though whether the latter is a benefit is open to question.
With the relocation kit fitted the air has a better route from the filter to the turbo. From what I can remember with a standard car the pipework flows like a reversed Z, with a couple of tight bends.
The only downside I can see is that with the relocation kit fitted the filter isn't securely fastened down. I originally had a panel filter that had some industrial Velcro holding it in place aided by some tie-wraps. When I swapped to the HKS filter, I couldnt used the backets supplied and had to hunt around for something else to fit the filter.
Hope this helps.